A typical known airfoil assembly includes an upper skin panel, a lower skin panel, and a number of composite spars interconnecting the upper and lower skin panels. The composite spars usually include a number of open-angle “C”-shaped spars (i.e., an angle of the upper flange or the lower flange at a web interface is slightly greater than 90°, making it an obtuse angle). Each open-angle spar faces (i.e., opens towards) either in the forward direction of the airfoil assembly or in the aft direction of the airfoil assembly depending upon the location of the particular spar. If the open-angle spar is located in a rear portion of the airfoil assembly, the spar generally faces forward of the airfoil assembly. If the open-angle spar is located in a front portion of the airfoil assembly, the spar generally faces in the aft direction of the airfoil assembly.
However, in some implementations of airfoil assemblies, a closed-angle spar (i.e., a spar where the upper flange, the lower flange, or both flanges develop an angle with the web that is less than 90°, making it an acute angle) is located in the front portion of the airfoil assembly. In these implementations, the closed-angle spar faces (i.e., opens towards) in the forward direction of the airfoil assembly like an open-angle spar located in the rear portion of the airfoil assembly. Accordingly, those skilled in the art continue with research and development efforts in the field of airfoil assemblies including composite closed-angle spars.